The present invention relates to an image reading apparatus for reading an image of a original placed on a transparent original placement surface, and an image reading head which is moved in a sub-scanning direction along the back side surface of a transparent original placement surface on which a original is placed and which detects light reflected from the original, and more particularly to an image reading apparatus capable of correcting for an influence of outside light, and an image reading head capable of being applied to the image reading apparatus.
An image reading apparatus for reading an image of a original by irradiating a original placed on a original placement surface with light from light emitting unit and sequentially detecting reflected light reflected by the original with respect to a plurality of scanning lines has been contemplated conventionally. In this type of image reading apparatus, when light from the outside of the image reading apparatus (the so-called outside light) enters the periphery of a original, the detection result of the reflected light is affected. Therefore, an related art proposes to provide a light amount detection sensor in the vicinity of a original placement surface and select luminance/density conversion table data according to an outside light level detected by the light amount detection sensor and correct the detection result of the reflected light based on the selected luminance/density conversion table data.